2. At standard atmosphere, it is a toxic gas with a pungent, irritating, and rotten smell. The triple point is 197.69 K and 1.67 kPa. It is released naturally by volcanic activity.
Sulfur dioxide was used by the Romans in winemaking when they discovered that burning sulfur candles inside empty wine vessels kept them fresh and free from vinegar smell.
https://en.wikipedia.org/wiki/Sulfur_dioxide
http://www.dummies.com/how-to/content/the-role-of-sulfites-in-wine.html
The pulp process involves many production stages, usually coupled with intermediate storage tanks. As each stage has a different reliability and bottlenecks may vary from day to day, scheduling a pulp mill needs to take into account these bottlenecks and the probability of a disturbance or breakdown. Each stage also may have different decision variables, such as steam / water / chemical input, etc.
https://en.wikipedia.org/wiki/Pulp_mill
http://www.gruvtroll.se/?p=23